fix(deps): update dependency postcss-rtl to v1.7.3 (#49)

Co-authored-by: Renovate Bot <[email protected]>

Author: renovate[bot]

package-lock.json

@@ -63,7 +63,7 @@
     "new-relic-source-map-webpack-plugin": "1.2.0",
     "node-sass": "4.13.1",
     "postcss-loader": "3.0.0",
-    "postcss-rtl": "1.5.0",
+    "postcss-rtl": "1.7.3",
     "react-dev-utils": "9.1.0",
     "resolve-url-loader": "3.1.1",
     "sass-loader": "6.0.7",